Walch et al. analyzed preoperative CT scans of 113 shoulders with primary glenohumeral osteoarthritis to characterize glenoid morphology. The central question: does humeral head position predict the pattern of glenoid erosion, and can dysplastic retroversion be distinguished from acquired posterior wear? The result was a three-type classification system that became the standard language for shoulder arthroplasty planning worldwide.
Every shoulder arthroplasty CT answers one question before you enter the OR: where is the humeral head, and what has it done to the glenoid over time? Type A glenoids tolerate standard components well, but watch for central bone stock loss in A2. Neer's rule requires at least 80% of the metal-backed component to contact good bone — central protrusion threatens this threshold.
Type B is where this classification changes your surgical plan. Posterior subluxation averaging 59% creates asymmetric horizontal-plane loading that produces rocking-horse loosening. Walch's group explicitly recommends earlier reconstruction in symptomatic Type B patients before the head becomes fixed posteriorly. Once it does, you are facing extensive soft-tissue release and bony reconstruction.
Type C retroversion above 25° is congenital dysplasia, not acquired wear. The key CT distinction: in Type C, the humeral head is centered (subluxation index ~55%) despite extreme retroversion; in B2, the head is posteriorly displaced and has carved out the biconcave deformity. Treating Type C like B2 with eccentric reaming alone ignores the underlying anatomy.
The Bercik modification (adding B3 and D subtypes) and the development of posterior-augmented glenoid components both trace their lineage directly to this classification framework.
Walch et al. analyzed preoperative CT scans of 113 shoulders with primary glenohumeral osteoarthritis to characterize glenoid morphology. The central question: does humeral head position predict the pattern of glenoid erosion, and can dysplastic retroversion be distinguished from acquired posterior wear? The result was a three-type classification system that became the standard language for shoulder arthroplasty planning worldwide.
Every shoulder arthroplasty CT answers one question before you enter the OR: where is the humeral head, and what has it done to the glenoid over time? Type A glenoids tolerate standard components well, but watch for central bone stock loss in A2. Neer's rule requires at least 80% of the metal-backed component to contact good bone — central protrusion threatens this threshold.
Type B is where this classification changes your surgical plan. Posterior subluxation averaging 59% creates asymmetric horizontal-plane loading that produces rocking-horse loosening. Walch's group explicitly recommends earlier reconstruction in symptomatic Type B patients before the head becomes fixed posteriorly. Once it does, you are facing extensive soft-tissue release and bony reconstruction.
Type C retroversion above 25° is congenital dysplasia, not acquired wear. The key CT distinction: in Type C, the humeral head is centered (subluxation index ~55%) despite extreme retroversion; in B2, the head is posteriorly displaced and has carved out the biconcave deformity. Treating Type C like B2 with eccentric reaming alone ignores the underlying anatomy.
The Bercik modification (adding B3 and D subtypes) and the development of posterior-augmented glenoid components both trace their lineage directly to this classification framework.